The dominant role of jetting in micron- and sub-micron sea spray produced by bubble bursting: A revised model and comparison with measurements

The size distribution of sub-micron sea spray aerosols (SSA) is a critical component of climate models, yet the primary physical mechanism governing their production – specifically the competition between film and jet droplets from bubble bursting – has remained a subject of intense debate. This work presents a revised, first-principles model to quantitatively resolve this controversy and demonstrate the dominance of jetting for producing micron and sub-micron aerosols. Our approach first rules out the film droplet mechanism as a primary contributor for this size range by demonstrating through physical scaling and numerical simulations that the final average ejected volume of sub-micron droplets is significantly smaller than that from jetting. We then construct a comprehensive global probability distribution function (PDF) for SSA by rigorously modeling its fundamental components in sequence: (i) refining the sub-surface bubble size distribution with a simpler and better experimentally supported exponential law, and (ii) deriving novel scaling laws for the number and size distribution of droplets per bursting event from a large set of high-resolution numerical simulations. A key finding is that the droplet size PDF from a single bubble follows a highly-skewed distribution – optimally modeled by a Generalized Inverse Gaussian distribution – revealing a prolific production of nanometric droplets previously unaccounted for by simpler models. When integrated, these components yield a final predictive model for the global SSA size distribution, with parameters derived directly from physical principles and simulations rather than empirical fitting. The model demonstrates strong predictive consistency, showing close qualitative agreement with a wide corpus of experimental data from both laboratory and oceanic measurements, particularly across the critical 25 nm to 2 . 5 μ m range. By clarifying that jetting is the dominant pathway and providing a robust, physically-grounded predictive tool, this research significantly enhances the fundamental understanding of marine aerosol generation and provides a more accurate foundation for climate and atmospheric chemistry models.